Comparison of Kernel Wax from Corn Genotypes Resistant or Susceptible to Aspergillus flavus

Abstract

Russin, J. S., Guo, B. Z., Tubajika, K. M., Brown, R. L., Cleveland, T. E., and Widstrom, N. W. 1997. Comparison of kernel wax from corn genotypes resistant or susceptible to Aspergillus flavus. Phytopathology 87: 529-533.Kernels of corn genotype GT-MAS: gk are resistant to Aspergillus flavus. Earlier studies showed that this resistance is due in part to kernel pericarp wax. Experiments were conducted to compare wax from GTMAS: gk kernels with that from kernels of several susceptible commercial hybrids. GT-MAS: gk had more pericarp wax than did the susceptible hybrids. Scanning electron microscopy revealed that GT-MAS: gk kernels appeared rough and showed abundant wax deposits on kernel surfaces. Susceptible kernels appeared much more smooth and lacked the abundant surface deposits observed in GT-MAS: gk. In vitro bioassays showed that kernel wax from GT-MAS: gk reduced A. flavus colony diameter by 35%. Colony diameters on a medium amended with wax from susceptible kernels did not differ from those of controls. Thin-layer chromatography and analyses of chromatograms using NIH Image software showed a distinctive composition for GT-MAS: gk kernel wax. Chromatograms of wax from GT-MAS: gk contained a peak unique to this genotype, but also lacked a peak common to all susceptible hybrids. This is the first report of specific kernel factors involved in resistance to A. flavus in corn.

Aflatoxin Resistance in Maize: What Have We Learned Lately?

“…Wax thickness and composition in the pericarp layer of the kernel have been reported to inhibit initial infection [61,90]. Recent microscopy studies of A. flavus hyphal growth inside inoculated maize kernels suggest barriers inside the kernel may also prevent spread through the hilar layer through which the A. flavus mycelia typically enters the kernel [91] or colonization within the kernel, in an apparent attempt to protect the embryo itself [92].…”

Development of Maize Host Resistance to Aflatoxigenic Fungi

“…The results of this study indicate the presence of two levels of resistance: at the pericarp and at the subpericarp level. The former was supported by the above-studies which demonstrated a role for pericarp waxes in kernel resistance [30], and highlighted quantitative and qualitative differences in pericarp wax between GT-MAS:gk and susceptible genotypes [31,32].…”

Crop Stress and Aflatoxin Contamination: Perspectives and Prevention Strategies

“…In order to utilize the resistance source of the GT-MAS:gk population associated with resistance, such as pericarp wax (Guo et al 1995(Guo et al , 1996Russin et al 1997 ) and antifungal proteins Chen et al 1998Chen et al , 2009 ) , Guo et al ( 2007Guo et al ( , 2011a released several inbred lines from this population with improved resistance and earliness. Resistance to afl atoxin accumulation has been attributed to the wax and cutin layers on the kernel pericarp (Guo et al 1995 ) , and this fi nding was confi rmed by Russin et al ( 1997 ) .…”